Silver halide color photographic materials are subjected to color development after exposure, which allows dye forming couplers to react with oxidation products of aromatic primary amine developing agents and form color images.
In this method, the color images are generally reproduced by the subtractive color process. In this process, couplers for forming yellow, magenta and cyan dyes are used Which are dispersed in silver halide emulsion layers different in color sensitivity. Of these couplers, acylacetanilide-type couplers such as pivaloyl-type yellow couplers, and benzoyl-type yellow couplers and malondianilide-type couplers are widely known as the yellow couplers.
The pivaloyl-type yellow couplers can provide excellent hue and color image fastness, and have been used mainly in color print materials. However, they exhibit the disadvantage of low molecular extinction coefficients and low coupling activities. Also with respect to hue and color image fastness, further developments have been desired to meet recently higher demands.
The benzoyl-type yellow couplers have been used mainly in negative films for shooting, because of their high molecular extinction coefficients and high activities. However, they are broad in their absorption wave forms and provide low fastness of formed dye images, such that further developments have also been desired.
The malondianilide-type yellow couplers are described, for example, in U.S. Patents 4,149,886, 4,095,984 and 4,477,563. They are inferior to the above-described benzoyl-type couplers in hue and image fastness. Therefore, they are only used as couplers of the development inhibitor releasing-type and have limited applications.
Couplers in which the disadvantages of the malondianilide-type couplers have been improved are described in European Patent 447020A1. However, even those couplers have not reached a fully satisfactory level in all of the color forming properties, hue and color image fastness.
There is a strong desire to develop couplers having a satisfactory combination of high molecular extinction coefficient, high color forming properties, excellent hue and the excellent color image fastness.
Various uses of high boiling organic solvents, antifading agents and color forming accelerators have been studied to compensate for the disadvantages of the yellow couplers of the types described above. For example, methods for improving the hue by use of high boiling organic solvents are described in JP-A-63-241547 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-63-256952, and methods for improving color image fastness are described in U.S. Pat. No. 4,745,049, JP-A-64-11262, JP-A-64-17056, JP-A-64-10247, JP-A-64-50048 and JP-A-2-4239. Methods for improving color image fastness by use of antifading agents are described, for example, in JP-A-61-2151, JP-A-61-6652, JP-A-l-196049 and JP-A-1-284853. Further, methods using water-insoluble, organic solvent-soluble polymers to improve the color image fastness are described in JP-A-64-50049.
However, materials or methods which can fully meet increasingly heightened demands have not yet been reached, even by the above-described methods. Further improvements in couplers, or techniques for use thereof, are still strongly desired.